Next generation of insect-control traits for corn

The next generation of insect-control traits from the seed corn industry will help growers deter yield loss, particularly from corn rootworm feeding.

“Historically, the main pests in corn have been corn rootworm and European corn borer,” says Clint Pilcher, DuPont Pioneer scientific affairs director. “Corn borers are not extinct, but we have seen a significant decrease in their overall population levels across the Corn Belt in recent years with increased use of Bt corn hybrids.

“Corn rootworms continue to be more problematic than corn borer, and growers will need to be more tuned into managing them with multiple modes of action in the future,” he adds.

The seed industry is now using multiple-mode-of-action traits to protect corn against insects. “The greatest benefit to customers will be products that have reduced refuge requirements and improved insect pest protection,” Pilcher states. “Farmers can plant these integrated products without also having to plant a separate refuge block with a non-Bt corn product.”

DuPont Pioneer

DuPont Pioneer recently released three insect-protection, single-bag integrated refuge products in corn. The company launched Optimum AcreMax and Optimum AcreMax Xtra in 2012. Optimum AcreMax XTreme was available on a limited basis this year and will be fully launched in 2013.

In the future, Pioneer plans to market more products with multiple-modes-of-action on above- and belowground insects, including corn rootworm, corn earworm, western bean cutworm, European corn borer, southwestern corn borer and black cutworm.

In the meantime, an integrated approach to managing corn insect pests such as corn rootworm is necessary to prevent resistance issues. “Using multiple tactics, including crop rotation, soil-, seed- and foliar-applied insecticides along with Bt corn options and their required non-Bt refuge plantings, are key to delaying corn rootworm resistance development to these transgenic products,” Pilcher says. “It is important to break the corn rootworm cycle, especially in high-pressure, continuous corn scenarios.”

Syngenta

New, multiple-mode-of-action, corn-insect trait stacks also will be readily available from Syngenta for 2013 and 2014, says Jill Wenzel, Syngenta commercial traits product lead. “Agrisure Viptera 3220 and Agrisure 3122 E-Z Refuge trait stacks are Syngenta’s first 5% integrated refuge products,” she says. “These new seed solutions help preserve trait technologies by stacking them and by making it easier for growers to comply with refuge requirements.”

Both products will be available from Syngenta’s Garst, Golden Harvest and NK seed brands for the 2013 planting season, Wenzel notes.

The Agrisure 3122 E-Z Refuge trait stack offers two modes of action for both above- and belowground insect protection. It combines the Herculex I trait, plus Agrisure CB/LL, to control corn borer and the Herculex RW and Agrisure RW traits to control corn rootworm.

“This product would be a particularly good option for areas planted into corn on corn,” Wenzel says. “One advantage to Agrisure 3122 is that neither mode of action that it relies on for corn rootworm control is one that Iowa State University recently confirmed to be resistant to western corn rootworm. So growers who are concerned that they might have corn rootworms that are becoming resistant to a trait developed by one of our competitors can use this Syngenta trait stack with confidence.”

Syngenta’s next-generation corn rootworm trait is Agrisure Duracade, which has already received EPA approval, but it is still waiting for USDA approval, Wenzel says. “It will be showcased next summer in a number of field trials where farmers can see it in action,” she says. “Agrisure Duracade will be launched in two, 5% refuge-in-a-bag products that will be available widely in the Corn Belt. Following receipt of all regulatory approvals, it is anticipated these new trait stacks will be sold in the fall of 2013, for planting in 2014.”

Wenzel adds that “a USDA study showed that [Agrisure Duracade] had 99%-plus reduction in adult beetle emergence, which is the highest beetle-reduction level ever recorded in their studies. [Another] significant point is that this product will have another, completely new mode of action (eCry3.1Ab).”

Looking ahead, Monsanto is employing “cutting-edge RNAi technology to incorporate an additional mode of action in our Corn Rootworm III project, which is currently in phase 3 of our pipeline,” Post says. “Corn Rootworm III will offer increased control and durability against the corn rootworm by providing three distinct modes of actions. Through the use of RNAi we’re able to target and control rootworms with a novel mode of action that’s outside of the Bt class of proteins that is used in all insect-control products today.”

The lead practice Monsanto recommends to growers is to rotate the field to a non-host crop such as soybeans, which breaks the corn rootworm cycle, Post says. “Another strong option is for growers to use Genuity SmartStax corn hybrids that provide dual-mode-of-action Bt traits and deliver excellent performance,” she adds. “If rotation or Genuity SmartStax corn is not an option for growers, using soil- or foliar-applied insecticides as needed to manage larvae and adults is a viable option.”